Condition Monitoring and Fault Detection of Blade Damage in Small Wind Turbines Using Time-series and Frequency Analyses

Condition monitoring systems are critical for autonomous detection of damage when operating remote wind turbines. These systems continually monitor the turbine’s operating parameters and detect damage before the turbine fails. Although common in utility-scale turbines, these systems are mostly undeveloped in distributed, small-scale turbines due to their high cost and need for specialized equipment. The Cal Poly Wind Power Research Center is developing a low-cost, modular solution known as the LifeLine system. The previous version contained monitoring equipment, but lacked decision-making capabilities. The present work builds on the LifeLine by developing software-based detection of blade damage. Detection is done by monitoring of tower vibrations, rotor speed, and generator power output. First, testing is completed to inform algorithm design: the tower vibrational response is recorded, and blade damage is simulated by adding a mass imbalance to one blade. From these results, several algorithms are developed, and their performance is analyzed in a cross-validation study. The time-series method known as the Nonlinear State Estimation Technique and Sequential Probability Ratio Test (NSET+SPRT) is implemented first. This algorithm is highly successful, with a 93.3% rate of correct damage detection; however, it occasionally raises false alarms during normal operation. A custom-built algorithm known as the Adaptive Fast Fourier Transform (AFFT) is also built; its strength lies in its elimination of false alarms. The final system utilizes a joint monitoring approach, combining the benefits of the NSET+SPRT and AFFT. The final algorithm is successful, correctly categorizing 95.5% of data when operating above 120RPM, and raising no false alarms in normal operation. This version is then implemented for live monitoring on the Cal Poly Wind Turbine, allowing for robust and autonomous detection of blade damage

A Physical Unclonable Function Based on Inter-Metal Layer Resistance Variations and an Evaluation of its Temperature and Voltage Stability

Keying material for encryption is stored as digital bistrings in non-volatile memory (NVM) on FPGAs and ASICs in current technologies. However, secrets stored this way are not secure against a determined adversary, who can use probing attacks to steal the secret. Physical Unclonable functions (PUFs) have emerged as an alternative. PUFs leverage random manufacturing variations as the source of entropy for generating random bitstrings, and incorporate an on-chip infrastructure for measuring and digitizing the corresponding variations in key electrical parameters, such as delay or voltage. PUFs are designed to reproduce a bitstring on demand and therefore eliminate the need for on-chip storage. In this dissertation, I propose a kind of PUF that measures resistance variations in inter-metal layers that define the power grid of the chip and evaluate its temperature and voltage stability. First, I introduce two implementations of a power grid-based PUF (PG-PUF). Then, I analyze the quality of bit strings generated without considering environmental variations from the PG-PUFs that leverage resistance variations in: 1) the power grid metal wires in 60 copies of a 90 nm chip and 2) in the power grid metal wires of 58 copies of a 65 nm chip. Next, I carry out a series of experiments in a set of 63 chips in IBM\u27s 90 nm technology at 9 TV corners, i.e., over all combination of 3 temperatures: -40oC, 25oC and 85oC and 3 voltages: nominal and +/-10% of the nominal supply voltage. The randomness, uniqueness and stability characteristics of bitstrings generated from PG-PUFs are evaluated. The stability of the PG-PUF and an on-chip voltage-to-digital (VDC) are also evaluated at 9 temperature-voltage corners. I introduce several techniques that have not been previously described, including a mechanism to eliminate voltage trends or \u27bias\u27 in the power grid voltage measurements, as well as a voltage threshold, Triple-Module-Redundancy (TMR) and majority voting scheme to identify and exclude unstable bits

From Safety Analysis to Experimental Validation by Fault Injection—Case of Automotive Embedded Systems

En raison de la complexité croissante des systèmes automobiles embarqués, la sûreté de fonctionnement est devenue un enjeu majeur de l’industrie automobile. Cet intérêt croissant s’est traduit par la sortie en 2011 de la norme ISO 26262 sur la sécurité fonctionnelle. Les défis auxquelles sont confrontés les acteurs du domaine sont donc les suivants : d’une part, la conception de systèmes sûrs, et d’autre part, la conformité aux exigences de la norme ISO 26262. Notre approche se base sur l’application systématique de l’injection de fautes pour la vérification et la validation des exigences de sécurité, tout au long du cycle de développement, des phases de conception jusqu’à l’implémentation. L’injection de fautes nous permet en particulier de vérifier que les mécanismes de tolérance aux fautes sont efficaces et que les exigences non-fonctionnelles sont respectées. L’injection de faute est une technique de vérification très ancienne. Cependant, son rôle lors de la phase de conception et ses complémentarités avec la validation expérimentale, méritent d’être étudiés. Notre approche s’appuie sur l’application du modèle FARM (Fautes, Activations, Relevés et Mesures) tout au long du processus de développement. Les analyses de sûreté sont le point de départ de notre approche, avec l'identification des mécanismes de tolérance aux fautes et des exigences non-fonctionnelles, et se terminent par la validation de ces mécanismes par les expériences classiques d'injection de fautes. Enfin, nous montrons que notre approche peut être intégrée dans le processus de développement des systèmes embarqués automobiles décrits dans la norme ISO 26262. Les contributions de la thèse sont illustrées sur l’étude de cas d’un système d’éclairage avant d’une automobile. ABSTRACT : Due to the rising complexity of automotive Electric/Electronic embedded systems, Functional Safety becomes a main issue in the automotive industry. This issue has been formalized by the introduction of the ISO 26262 standard for functional safety in 2011. The challenges are, on the one hand to design safe systems based on a systematic verification and validation approach, and on the other hand, the fulfilment of the requirements of the ISO 26262 standard. Following ISO 26262 recommendations, our approach, based on fault injection, aims at verifying fault tolerance mechanisms and non-functional requirements at all steps of the development cycle, from early design phases down to implementation. Fault injection is a verification technique that has been investigated for a long time. However, the role of fault injection during design phase and its complementarities with the experimental validation of the target have not been explored. In this work, we investigate a fault injection continuum, from system design validation to experiments on implemented targets. The proposed approach considers the safety analyses as a starting point, with the identification of safety mechanisms and safety requirements, and goes down to the validation of the implementation of safety mechanisms through fault injection experiments. The whole approach is based on a key fault injection framework, called FARM (Fault, Activation, Readouts and Measures). We show that this approach can be integrated in the development process of the automotive embedded systems described in the ISO 26262 standard. Our approach is illustrated on an automotive case study: a Front-Light system

Erfassung und Evaluierung von Teilentladungen in Leistungstransformatoren mit speziellen Sensoren und Diagnoseverfahren

Transformers are key elements of the power grid. Due to their importance and high initial cost, asset managers utilize monitoring and diagnostic tools to optimize their operation and extend their service life. The main objective of this thesis is to develop new methods in the field of monitoring and diagnosis of transformers in order to reduce maintenance costs and decrease the frequency of forced outages. For this purpose, two concepts are proposed. Small generator step-up transformers are essential in wind and photovoltaic parks. The first presented concept entails an online fault gas monitoring system for these transformers, specially hermetically-sealed transformers. The developed compact, maintenance-free and cost-effective monitoring system continuously tracks the level of the key leading indicators of transformer faults in the gas cushion. The second presented concept revolves around partial discharge (PD) assessment by the UHF measurement technique, which is based on capturing the electromagnetic (EM) waves emitted in case of PD in the insulation of a transformer. In this context, the complex EM system established when probes are introduced into the tank of a transformer and with PD as the excitation source is analyzed. Drawing on this foundation, a practical approach to the detection and classification of PD with the focus on the selection of the optimal frequency range for performing UHF measurements depending on the device under test is presented. The UHF measurement technique also offers the possibility of PD localization. Here, the determined arrival time (AT) of the captured signals is critical. A PD localization algorithm, based on a multi-data-set approach with a novel AT determination method, is proposed. The methods and algorithms proposed for the detection, classification and localization of PD are validated by means of practical experiments

Neutral Gas and Plasma Interactions in the Polar Cusp

When the solar wind interacts with the Earth's magnetosphere, both energy and matter can be transferred across the magnetopause boundary. This transfer gives rise to numerous phenomena, including ion outflow and neutral upwelling in the polar cusps. These processes are caused by a transfer of energy to the ionospheric plasma and neutral gas through various mechanisms. The heated plasma or gas expands, increasing the density of the atmosphere at high altitudes by as much as a factor of two, and injecting ionospheric plasma into and even outside of the magnetosphere. These two phenomena are examined in two ways: A novel high energy (0.1--10 keV) spectrograph for ionospheric cusp ions was designed as part of the Rocket Experiment for Neutral Upwelling (RENU), a sounding rocket campaign carried out at the northern polar cusp to observe the electrodynamic properties of the cusp during a neutral upwelling event. This instrument is called the KeV Ion Magnetic Spectrograph (KIMS). Ion outflow in the ionosphere has shown evidence of correlation with both Poynting flux and soft electron precipitation in the cusp. The heat input from these energy sources might also affect neutral gas in the ionosphere, contributing to upwelling phenomena seen at the dayside cusp. Using data from the Fast Auroral Snapshot Explorer (FAST) and the Challenging Minisatellite Payload (CHAMP) satellites, correlations of electromagnetic and particle energy inputs are examined with both ion outflow and neutral upwelling in the cusp. The added ability to process large quantities of data quickly and reference the data between separate satellites in this statistical survey gives clues to the consistency of the observed correlations with ion outflow over time and to the relative importance of these energy sources in the neutral upwelling phenomenon. It also provides the ability to understand these connections in a broad spectrum of conditions of the Sun and solar wind as well as in the Earth's magnetosphere

Development of a Mars Exploration Rover for RASC-AL Exploration RoboOps Competition with an Extended Kalman Filter Based Navigation System

The primary objective of this research is to develop a navigation system for use on a rover designed for the NASA-NIA Revolutionary Aerospace Systems Concepts Academic Linkage (RASC-AL) Exploration RoboOps challenge. This competition takes place at NASA\u27s Johnson Space Center Rock Yard, a test facility with many obstacles including steep hills, craters, rocks and loose sandy terrain. In addition to the challenges of the terrain, the rover\u27s operators must control it from West Virginia University\u27s campus. It was observed during the 2012 competition that a primary challenge was a lack of situational awareness; the operators had to navigate the large test area with only delayed video from two low resolution cameras. This research seeks to provide better awareness of the rover\u27s position in the rock yard through the development of an accurate navigation assistance system.;This research first presents the rover that was designed, developed, and demonstrated at the 2012 competition that features six-wheel-drive, four-wheel steering, and a rocker-bogie suspension system similar to NASA rovers currently operating on Mars.;This research then presents a Navigation Assistance System (NAS) capable of providing nine-state navigation data, using small, lightweight, and low-cost sensors. In order to achieve an optimal estimate of the rover\u27s attitude, velocity, and position this system employs an Extended Kalman Filter (EKF) that fuses data from an Inertial Measurement Unit (IMU) and a Global Positioning System (GPS). The EKF utilizes complimentary data from both systems to minimize the degradation caused by inherent system error that would be experienced by using either system alone.;The primary output of the NAS, position, is evaluated against a high-quality dual-antenna, Differential GPS (DGPS) receiver, as well as a low-cost single antenna GPS receiver. The NAS was observed to provide smoother position output, however actual error from the DGPS was only slightly reduced; in the nominal case an improvement of 0.2 meters was observed. Furthermore, testing demonstrated that the overall accuracy of the GPS alone, in comparison with the DGPS unit, was observed to be 1.7 meters. For the intended purposes of the system, it was found that using GPS alone would be sufficient for navigation applications.;The integration of this system with the rover brought unexpected challenges stemming from electrical interference created by on-board electronics, therefore this work presents the results of the navigation assistance system development taken off-board the rover. Furthermore, it presents research on autonomous navigation algorithms that could implement the state estimation data provided by the navigation assistance system that was developed